Tolylene diisocyanates stabilized with 1-phenyl-2-thiourea



United States Patent 3,281,446 TOLYLENE DIISOCYANATES STABILIZED WITH1-PHENYL-2-THIOUREA David T. Manning, South Charleston, W. Va., assignorto gnion Carbide Corporation, a corporation of New ork N0 Drawing. FiledMay 9, 1963, Ser. No. 279,335 2 Claims. (Cl. 260453) This inventionrelates to isocyanate compositions, particularly an isocyanatecomposition stabilized from discoloration.

Isocyanates are typically colorless liquids or solids which are found todiscolor on storage. Discoloration of isocyanates deleteriously affectstheir saleability typically because the color may be transferred to theproduct in which the isocyanate is employed. This is particularly so inthe case of polyisocyanates used in resin manufacture.

It is herein provided an agent which significantly retards discolorationof the isocyanate product thus allowing storage of the isocyanate forreasonable periods of time prior to use. These agents are particularlyeffective when employed in solution with the isocyanate.

The agents employed in this invention for retarding discoloration oforganic isocyanates are organic thioureas possessing one nitrogen atombearing two hydrogen atoms, the other nitrogen :atom bearing at leastone directlybonded aromatic ring. Of particular significance arethioureas having the formula:

wherein R and R may be hydrogen; alkyl of from 1 to 18 carbon atoms,preferably of from 1 to 12 carbon atoms; cycloalkyl, preferably of from5 to 8 carbon atoms; aryl, preferably monocyclic, bicyclic aryl andfused aryl; alkenyl of from 2 to 18 carbon atoms, preferably of from 2to 8 carbon atoms; cycloalkenyl, preferably of from 5 to 8 carbon atoms;alkoxy of from 1 to 18 carbon atoms, preferably of from 1 to 12 carbonatoms; aryloxy, preferably monocyclic and bicyclic aryloxy; halogen,such as chlorine, bromine and fluorine; R can be hydrogen, alkyl of from1 to 12 carbon atoms, alkenyl of from 2 to carbon atoms, cycloalkyl offrom 5 to 8 carbon atoms or and preferably hydrogen; n is an integer offrom 0 to 5; m is an integer of from 0 to 5; and the sum of n and m isequal to 5.

Exemplifications of the aforementioned class of thioureas includel-phenyl-Z-thiourea,

1- Z-methylphenyl) -2-thiourea,

1t- (2,4-diethyl-phenyl -2-thiourea,

1- 3-butylphenyl -2-thiourea, l-(4-octadecylphenyl -2-thiourea, l-( 1-naphthyl -2-thiourea,

1- (Z-naphthyl -2-thiourea, l-(phenanthryl -2-thiourea,

1-( 1 -benzanthryl -2-thioure a, 1-(4-vinylphenyl) -2-thiourea,

1- [3 (Z-butenyl phenyl] -2-thiourea, 1- [4- S-hexenyl phenyl]-2-thioure a, 1- (4-vinyl-3-methylnaphthyl) -2-thiourea,

3,281,446 Patented Oct. 25, 1966 Ice 1- (4-cyclohexylphenyl) -2-thiourea,

1- [4- 3 -cyclohexenyl phenyl -2-thiourea, 1- Z-methoxyphenyl-2-thiourea,

1- Z-phenoxyphenyl -2-thio-urea,

1- (4-butoxynaphthyl -2-thiourea, 1t-(2-chl0rophenyl)-2-thiourea,

1-( 4-bromonaphthyl -2-thiourea,

1- S-fiuorophenanthryl -2-thiourea, l-phenyl- 1 -methyl-2-thiourea,

l-phenyl- 1 -butyl-2-thiourea,

l- Z-methylphenyl) l Z-ethylhexyl -2-thiourea, 1- l-n-aphthyl l3-butenyl -2-thiourea, 1- (4-vinylphenyl) -1-cycloheXyl-2-thiourea,l-phenyl- 1 -cycloheptyl-2-thiourea, bis(1-phenyl)-2-thiourea,

bis[ 1- (Z-methylphenyl) ]-2-thiourea,

bis( lr-phenanthryl -2-thiourea, bis[1-(3-butenyl-2-phenyl)]-2-thiourea,

and the like. 2-thiourea.

The isocyanates which may be treated to retard discoloration are organicmonoand polyisocy-anates, such as aliphatic, cycloaliphatic and aromaticmono-, di-, triand/or other poly isocyanates which tend to discolorunder conditions of moisture and temperature typically associated withindustrial storage procedures. Illustrative of organic isocyanates whichare beneficially stabilized from discoloration include the following:

The most preferred thiourea is l-phenyl- The particular colorretardation agent selected (color stabilizing agents) should be capableof dissolution in the particular isocyanate to be stabilized regardlessof whether the isocyanate is a liquid at ambient temperature or must bewarmed to transform it to the liquid state. The selected agent should bestable at the temperature of the isocyanate at the time ofincorporation, and incorporation be effected at a temperature below thatof decomposition or of any undesirable reaction of the isocyanate withitself or the agent. The agent, or mixtures of the agents, should beemployed in the isocyanate in any amount sufficient to retarddiscoloration. Usually that amount falls between 0.005 and 5 percent byweight of the isocyanate. Preferably, the agent is employed in amountsfrom about 0.01 to 1.0 percent by weight of isocyanate. In general, thisinvention is directed to employing an amount of the agent sufficient toretard discoloration of the isocyanate.

The following serves to specifically illustrate operation of thisinvention, however, it is not intended to limit the scope of thisinvention:

A dry 8-ounce glass bottle is purged with dry nitrogen and charged witha mixture of 150 grams of colorless, pure, freshly-distilled tolylenediisocyanate (80 weight percent 2,4-tolylene diisocyanate and 20 weightpercent 2,6-tolylene diisocyanate) and 0.15 gram of 1-phenyl-2-thiourea. The resulting composition is blanketed under dry nitrogen andthe bottle securely sealed by wrapping its stopper with tape. A similarsample is repared, but without the added 1-phenyl-2-thiourea, for use asa blank.

Both the blank and the l-phenyl-Z-thiourea test samples are stored inthe dark at room temperature, about 25 C. Examination of the blank andthiourea samples after storage for 22 days reveals the development of asignificantly deeper yellow color in the blank. After 5 /2 months, thel-phenyl-Z-thiourea sample is unchanged 4 and exhibits a significantlyweaker yellow color than did the blank after only 22 days of storage.

Though the above relates to specifics of the present invention, thisinvention is not intended to be restricted thereby except insofar asthese specifics appear in the claims.

What is claimed is:

1. A solution of tolylene diisocyanate and from about 0.005 to 5 percentby weight of said diisocyanate of 1 phenyl-Z-thiourea.

2. A solution of tolylene diisocyanate and from about 0.01 to 1.0percent by weight of said diisocyanate of 1- phenyl-2-thiourea.

References Cited by the Examiner UNITED STATES PATENTS 2,885,421 5/1959Spiegler 260453 CHARLES B. PARKER, Primary Examiner.

IRVING MARCUS, JOSEPH P. BRUST, Examiners.

DALE R. MAHANAND, Assistant Examiner.

1. A SOLUTION OF TOLYLENE DIISOCYANATE AND FROM ABOUT 0.005 TO 5 PERCENTBY WEIGHT OF SAID DIISOCYANATE OF 1PHENYL-2-THIOUREA.